1. Field
The following description relates generally to wireless communications, and more particularly to managing access control to Closed Subscriber Group (CSG) cells in a wireless communication environment.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as, for example, voice, data, and so on. Typical wireless communication systems can be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, . . . ). Examples of such multiple-access systems can include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like. Additionally, the systems can conform to specifications such as third generation partnership project (3GPP), 3GPP long term evolution (LTE), ultra mobile broadband (UMB), and/or multi-carrier wireless specifications such as evolution data optimized (EV-DO), one or more revisions thereof, etc.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple user equipments (UEs). Each UE can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to UEs, and the reverse link (or uplink) refers to the communication link from UEs to base stations. Further, communications between UEs and base stations can be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth. In addition, UEs can communicate with other UEs (and/or base stations with other base stations) in peer-to-peer wireless network configurations.
Heterogeneous wireless communication systems commonly can include various types of base stations, each of which can be associated with differing cell sizes. For instance, macro cell base stations typically leverage antenna(s) installed on masts, rooftops, other existing structures, or the like. Further, macro cell base stations oftentimes have power outputs on the order of tens of watts, and can provide coverage for large areas. The femto cell base station is another class of base station that has recently emerged. Femto cell base stations are commonly designed for residential or small business environments, and can provide wireless coverage to UEs using a wireless technology (e.g., 3GPP Universal Mobile Telecommunications System (UMTS) or Long Term Evolution (LTE), 1× Evolution-Data Optimized (1×EV-DO), . . . ) to communicate with the UEs and an existing broadband Internet connection (e.g., digital subscriber line (DSL), cable, . . . ) for backhaul. A femto cell base station can also be referred to as a Home Evolved Node B (HeNB), a Home Node B (HNB), a femto cell, or the like. Examples of other types of base stations include pico cell base stations, micro cell base stations, and so forth.
In some scenarios, some femto cell base stations or other base stations in a network can be restricted for access in some manner. For example, different base stations in the network can belong to different Closed Subscriber Groups (CSGs). In various situations, access control issues can arise due to a lack of synchronization between a UE and a network. More particularly, a UE can use some form of list (e.g., whitelist, . . . ) to identify base stations that the UE is allowed to access. The list retained by the UE can be read only and operator controlled. Further, the network can have an equivalent list. A problem can arise if the UE is removed from a CSG. For example, if the UE is removed from a CSG, and the list stored by the UE is not updated before the UE attempts to access a CSG cell from the CSG, then the UE can receive a reject message indicating that the UE lacks authorization for this CSG. Further, since the list stored by the UE is read only, the UE can be unauthorized to change entries in the list stored by the UE, and thus, unable to remove the CSG from such stored list. With the CSG still included in the list stored by the UE, the UE can again attempt to access the CSG cell from the CSG, and again receive a reject message indicating that the UE lacks authorization for this CSG.